Homeowners and turfgrass managers in the United States rely on fewer than 20 plant species for all their grassing needs. Moreover, nearly all of these 20 grasses originate from the same general region of Eurasia. An estimated 46.5 million acres of turfgrasses are presently grown in the US (Grounds Maintenance magazine, May 1996, p. 10.). Concentrating this few number of species over a vast agricultural landscape is bound to produce problems over time as disease or insect organisms build up and become virulent against existing grasses. This type of pandemic actually occurred in the US in recent years, when large acres of the corn belt were decimated by an outbreak of southern corn leaf blight when a mutated strain of the disease arose.
The solution to this dilemma lies in species diversity. Agriculturists have found that by increasing the number and breadth of species, there is increased genetic diversity and less chance that a particular parasite will devastate a substantial acreage of plants.
Another factor urgently needed is diversity in where species originate. Most of the common turfgrasses grown in this country--Kentucky bluegrass (Poa pratensis L.), creeping bentgrass (Agrostis stolonifera L.), fine fescue (Festuca spp.), tall fescue (F. arundinacea Schreb.), and perennial ryegrass (Lolium perenne L.)--species that comprise the bulk of turf in the temperate zone--derive from the same region of Europe. Only one turfgrass species originates from here in North America (Buchloe dactyloides [Nutt.] Engelm.) and only two from Eastern Asia (Zoysia japonica Willd. and Eremochloa ophiuroides [Munro.] Hack). To increase the breadth of genetic origin, more turfgrasses are needed that originate from a broader sector of world geography, to bolster the diversity of today's turfgrasses.
Another advantage of seeking out additional turf species is to help reduce turf maintenance levels. Present-day turfgrasses are better suited to high maintenance than low. They perform best when given a steady diet of water, fertilizer, and chemical pesticides. In theory, grasses native to a particular locale should be able to withstand local growing conditions better than exotics, without the need for additives and preservatives. Grass species that can survive on less input of water or other scarce natural resources offer benefits for reducing maintenance and improving environmental friendliness of lawns.
But finding and developing new grass species from nature is difficult, time consuming, and expensive. The developer must sift through thousands of prospective grasses listed in botanical literature, identify promising grasses, and travel thousands of miles to locate, isolate, identify, transport, quarantine, grow, test, and breed these grasses. This process can take more than 10 years to develop acceptable cultivars. Furthermore, as it turns out, most prospective grasses in nature have no commercial turf value, due to their inability to generate an acceptable ground cover when mowed. The vast majority of natural grasses cannot produce a plush lawn under continuing defoliation.
Also, few grasses found in nature have the ability to produce marketable quantities of seed--a critical necessity for commercialization of a new grass species. Raw germplasm of most native grasses seldom tops 100 lbs. per acre in seed production (R. S. Sadasivaiah and J. Weijer, 1981, The utilization of native grass species for reclamation of disturbed land in the alpine and subalpine regions of Alberta. In Reclamation in mountainous areas. Proc. 6th ann. meeting Can. Land Reclam. Assoc.); this level of production is not high enough for economic viability. By contrast, popular grasses like tall fescue have been cultivated and selected since prehistoric times for cattle fodder. Only high yielding plant lines have persisted through the ages. Many of today's tall fescue cultivars top 1 ton per acre in seed production.
Yet another complexity facing the plant developer is the unresponsiveness of many wild grasses to plant breeding. The vast majority of wildland grasses lack genetic potential for refinement into desirable turfgrass cultivars. Only after considerable investment in collection and breeding does the developer discover which grass species can be successful bred and which cannot.
Eastern China is the center of origin for three zoysia species: Z. japonica, Z. sinica, and Z. macrostachya. Zoysia japonica, commonly known as Japanese zoysia, is a popular turfgrass in the Asia Pacific Rim countries and in the US mid-Atlantic region. Several vegetatively propagated cultivars have been developed from this species, including `Meyer,` `El Toro,` `Belair,` and `Midwest.` All of these cultivars are clonally propagated by means of vegetative cuttings. Only in recent years has there been effort to develop seeded cultivars of Z. japonica, due to the fact that breeding of the species is slow and tedious (S. H. Samudio, 1996, Whatever became of the improved seeded zoysia varieties? Golf Course Mgmt. August 1996, p. 57-60). Only two seeded Z. japonica cultivars, `W3-2` and `Zenith,` have been sold commercially.
To date, Zoysia sinica Hance and Zoysia macrostachya Franch. et Sav. have never been commercially developed. In China and its neighboring countries, these two grasses are native to the seashore. They are found along coastal plains with seawater often washing their roots. Scientists have speculated that these two grasses may be halophytes--plants that actually require salt as part of their metabolism (K. B. Marcum, M. C. Engelke, and S. J. Morton, 1993, Salt tolerance and associated salt gland activity of zoysiagrasses, Agronomy Abstr., Amer. Soc. Of Agronomy, Madison, Wis.). Hence, these species hold the potential for soil stabilization in areas of high salt soils or saline irrigation water. More and more, salt intrusion is becoming a concern in many areas of the US, including Florida, Texas, and most of the West.
Zoysia sinica has no common (English) name. Therefore, the name "seashore zoysiagrass" is proposed for this species to designate its seaside origins.
Vegetatively, seashore zoysiagrass is quite similar in appearance to Japanese zoysia. The main differentiating point is seed length. Seed of Z. sinica are about twice as long as those of Z. japonica, making identification possible even with a single seed.
Quantities of Chinese common zoysia seed have been produced and imported into the US in recent years. While most of this seed is Z. japonica, a minute amount is Z. sinica and Z. macrostachya. Chinese zoysia seed is hand-harvested in the wilds, throughout mountains and along the seashore. Although the harvesters are pursuing the much-sought-after Z. japonica seed, they sometimes inadvertently harvest patches of Z. sinica or Z. macrostachya. Hence, a small amount of Z. sinica makes its way into this country each year, albeit incognito.
Dong and Chen (L. S. Dong and B. X. Chen, 1991, Zoysia germplasm resource investigation in the Jiaozhou Bay, Qingdao Lawn Construction Development Co., Qingdao, Shandong, PRC) characterize Z. sinica as:
Root-shaped creeping stems, and height of 7-15 cm, thread-shaped coniferous leaves with hard textures and a length of 3-7 cm and a width of 3 mm. The leaf edges bent inward with long soft hairs around the leaf sheath, the ligule is a circle with long soft hairs, the total ear length is 3-4 cm and the width, 2 mm. The spikelet is light purple with a length of 3-4 cm and a width of 1.5 mm and coniferous leaves. The stem of the spikelet is 1-2 mm. The blooming stage is May-July and the seed-setting time is July-August.
In Korea, Hong et al. (K. Hong, H. Yeam, and Y. Do, 1985, Studies on interspecific hybridization in Korean lawngrass [Zoysia spp.], J. Korean Soc. of Hort. Sci. 26(2):169-178) describe Z. sinica as being taller growing than Z. japonica. And they found differences between the two species in their natural occurrence. They describe the indigenous habitat of Z. japonica as inland "fields," versus the habitat of Z. sinica as the "slime along the shore." Hong et al. characterized the average seed length of Z. sinica as 5.3 mm, compared to 2.4 mm for Z. japonica. The leaf width of Z. sinica was a finer 2.9 mm, versus 5.1 mm for Z. japonica. They found that Z. sinica was capable of producing viable seed when pollinated with Z. macrostachya, suggesting a genetic connection between the two species.